Page:De Vinne, Invention of Printing (1876).djvu/67

Rh would lead to fatal faults in inaccuracy of body. Exactness of body can be had only by casting all the characters in one mould, but this mould must be made to suit all the matrices. The matrices must be frequently changed, but with such nicety that the types of every letter shall be uniform in height, in line, and truly square. Any mechanic will see that the construction of an adjustable mould is work of difficulty, and that the fitting-up of a set of matrices for one mould is a very nice operation.

The Type-Mould of modern type-founders consists of two firmly screwed combinations of a number of pieces of steel, making right and left halves. In the first illustration of the mould, Figure 1, the halves are properly connected. In this form it is not practicable to represent the interior, but it may be understood that the interior faces fit each other snugly in every part but the centre, in which provision is made for a small opening which can be increased or diminished in a lateral direction only. One end of this opening is closed by the matrix; the other end is the jet, or the mouth-piece through which the melted metal is injected. In this opening, which is indicated by the letter H in the cut, the body of type is cast. The matrix which forms the face of the type is snugly fitted between the jaws on